David Kay, who led the search for banned weapons of mass destruction in postwar Iraq, said on Monday in an opinion piece in The Washington Post that there was "an eerie similarity to the events preceding the Iraq war".
"What is in doubt is the ability (of) the US government to honestly assess Iran's nuclear status and to craft a set of measures that will cope with that threat short of military action by the United States or Israel," Kay added.
US President George Bush justified the March 2003 invasion of Iraq by saying Saddam Hussein posed a threat because Baghdad had stockpiles of chemical and biological weapons and was reviving its nuclear weapons programme.
No such weapons were found. Kay told the Senate Armed Services Committee a year ago that US intelligence was "almost all wrong," and later urged reorganisation of the US intelligence services.
Cheney statement against Iran
recently triggered concern
The US government accuses Tehran of pursuing nuclear weapons under the guise of a civilian nuclear energy programme, a charge Iran denies.
Remarks by top US officials including Vice President Dick Cheney recently stirred concern of possible military action against Iran, which Bush has called the "world's primary state sponsor of terror."
However, the administration, including Secretary of State Condoleezza Rice and Defence Secretary Donald Rumsfeld, has since stressed diplomacy with in public comments.
"Now is the time to pause and recall what went wrong with the assessment of Iraq's WMD programme and try to avoid repeating those mistakes in Iran," Kay said in the Post.
He suggested Washington accept that it cannot prevent Iran from possessing the scientific knowledge for developing a nuclear weapon.
"It is nonsense to talk about eliminating Iran's nuclear capabilities short of war and occupation," said Kay, who urged the administration to rely on UN weapons inspectors to uncover any future weapons violations.
"It is nonsense to talk about eliminating Iran's nuclear capabilities short of war and occupation"
former UN weapons inspector
"The goal ... is to craft a set of tools and transparency methods that so tie Iran's nuclear activities to the larger world of peaceful nuclear activities that any attempt to push ahead on the weapons front would be detectable."
Kay recommended that the administration safeguard the quality of its intelligence on Iran by involving respected outside experts in its assessment.
He also warned that the United States would only invite international derision by relying Iranian exiles for material to support its case, as it relied on Iraqi expatriates in 2003.